The built-up or layered asphalt roof is commonly used in present construction methods and over two billion square feet of such roofing is installed annually. Some 10 to 15 percent of this total roof area requires additional maintenance for various reasons, one of the most important being the occurrence and growth of blisters therein, which expand and separate the roof plies, creating an unsightly appearance and increasing the risk of injury to the roof.
In a conventional built up asphalt roof construction, for example, a membrane is the basic component thereof and may be composed of at least two felt and asphalt or bitumen plies protected by a top coat of asphalt with mineral aggregate or crushed rock spread thereover. Such a roof is constructed like a multi-deck sandwich, and include a base ply sheet either nailed to the structural roof or cemented thereto with a thin layer of asphalt. On top of the base ply sheet, one or more layers of asphalt impregnated roofing felts are applied as by laying in strips with overlapping edges and cemented down by an asphaltic coating. Finally, a top coat is applied to form the completed membrane and is generally a relatively heavy layer of built up roofing asphalt with the mineral aggregate surface spread thereover. Additionally, such roof construction methods often include a layer of insulating material between the membrane and the structural roof to reduce heat transfer between the exterior and the building interior to which the above membrane is applied.
Blisters pose significant problems for the built-up membrane and are one of the major reasons calling for membrane maintenance. The blisters can range in size from virtually indetectable spongy spots to bloated spaces of one foot in height, and covering as much as fifty square foot in area. This can be caused by heated water vapor entrapped principally between the plies but at times between the substrate and the membrane.
The present invention contemplates applying a quantity of petroleum hydrocarbon to the blistered portions of the roof membrane. The petroleum hydrocarbon is of such a nature, hereinafter described, that in the particular mode of application it penetrates the top coat and softens the separated plies and instills self-healing properties in the asphalt thereof whereby the same can be directed back into rebonding by physical contact.
The principle objects of the present invention are: to provide a method for reduction and repair of blisters in asphalt roofs; to provide such a method which effectively rebonds separated plies; to provide such a treatment which heals cracked top coat roof surfaces; to provide such a treatment wherein a liquid petroleum hydrocarbon is applied to the blistered and weathered portion of roof membranes, thereby penetrating and softening the same and permitting the separated plies or top coat surface cracks to move into rebonding contact; to provide such a treatment softening and instilling proper self-healing properties into the asphalt of the roof membrane whereby the asphalt flows into resealing and rebonding contact under normally encountered temperatures and pressures; to provide such a treatment facilitating ease of maintenance of asphalt roof coverings; and to provide such a method which is relatively inexpensive, highly reliable in use, and well adapted for its intended purpose.